1. Field of the Invention
The present invention relates, in general, to seats, and, more specifically, to power seat adjusters for automobile seats.
Powered seat adjusters are a popular option on many automotive vehicles and are frequently offered as standard equipment on higher priced vehicles. Such power seat adjusters are primarily used on the driver's seat and, sometimes, on the front passenger seat of the vehicle.
Such power seat adjusters carry an upper support frame which supports the seat bottom and sometimes the seat back of the vehicle seat. The upper support frame is mounted on first and second, spaced track assemblies, each formed of an upper track which is connected to the upper support frame and which is slidably mounted in a lower track anchored to the vehicle floor. A drive mechanism, typically formed of a bi-directional electric motor, is mounted on the power seat adjuster and rotates a pair of drive shafts extending outward from the motor to a gear assembly or box mounted in each upper track. In one arrangement, the gear box rotates a lead screw extending below each upper track. A drive block mounted to the lower track threadingly receives the lead screw to cause reciprocal movement of the upper track and the attached upper support frame upon selective energization of the drive motor. Other drive mechanisms may also be incorporated into the power seat adjuster to provide vertical movement of the seat frame as well as pivotal movement of the seat back with respect to the seat bottom.
Although such power seat adjusters provide easy fore and aft movement of the seat in the lower tracks, it is imperative that the seat remain in a fixed, stationary position during a collision in order to prevent injury to the vehicle passenger using the seat. As a result, the weight and size of the power seat adjuster components are selected to provide a maximum amount of strength to resist any movement under the high impact forces transmitted to the seat from occupant and seat weight inertial loads and, sometimes, through the seat belt during a vehicle collision. Thus, the individual tracks, the torsion tubes or bars typically extending between and interconnecting the spaced upper tracks into a rigid structure and the other components of the power seat adjuster are made with stronger materials and greater thicknesses and dimensions to provide the requisite amount of strength. Although this adds weight and cost to the seat, such efforts have been considered essential to provide adequate strength to the seat to resist movement of the seat during a vehicle collision.
In previously devised upper tracks in a power seat adjuster, separate brackets or flanges have been attached to each upper track to attach various components to the upper tracks, such as to provide attachment of torsion tubes or bars to each upper track. A separate bracket was also employed to mount the metal gear box to the upper track. Such brackets are attached to the upper tracks by welding, or by means of various fasteners, such as rivets, screws, etc. However, the use of separate mounting brackets to attach the torsion tubes to the upper tracks and the processes required to attach such mounting brackets to the upper tracks results in the formation of metallurgical changes or stress risers in the structure of the upper tracks which weaken the upper tracks and could lead to a failure and movement of the upper tracks of the power seat adjuster and thereby the seat and the user during a vehicle collision. Welding utilizes high heat levels which cause metallurgical and dimensional changes in the structure of the upper tracks and can lead to a significant decrease in the strength of the upper tracks. Further, the formation of apertures in the mounting brackets and upper tracks to receive rivets, screws, etc., to attach the mounting brackets to the upper tracks creates stress risers which weaken the structure of the mounting bracket and the upper tracks and can lead to premature failure and separation of the mounting bracket from the upper track.
The horizontal drive mechanism employed to reciprocally move each upper track within a lower track typically includes a gear box attached to the upper track and coupled to the output shaft of the horizontal drive motor to transmit rotation of the output shaft of the drive motor to rotation of the lead screw which, through threading interaction with the drive block attached to the lower track, results in a sliding movement of the upper track with respect to the associated lower track. In order to provide adequate strength, the gear box has been formed of large zinc die castings. Such a construction has been considered necessary to provide adequate strength to the power seat adjuster to resist movement or deformation of the gear box during high impact loads, such as loads occurring a vehicle collision. However, such castings are costly and heavy. Further, the metal-to-metal contact of the gears generates undesirable noise and can create vibrations which are transmitted through the metal components of the power seat adjuster directly to the user of the seat.
Thus, it would be desirable to provide a power seat adjuster which has a lighter weight and fewer components than previously devised power seat adjusters which still retaining sufficient strength to resist movement of the power seat adjuster during impact loads occurring during a vehicle collision. It would also be desirable to provide a power seat adjuster which eliminates additional mounting brackets and associated welding and fastener mounting operations employed in previously devised power seat adjusters to attach the torsion tubes to the movable upper tracks of the power seat adjuster. Finally, it would be desirable to provide a power seat adjuster which has a reduced weight and a lower cost as compared to previously devised power seat adjusters.